Projection lens device and projection display apparatus using the same

Abstract

A projection lens device includes, in order from a magnification side, a first lens group G 1 having a negative refractive power, and a second lens group G 2 having a positive refractive power. The projection lens device is substantially telecentric on a reduction side thereof. The second lens group G 2 includes a three-element cemented lens L 10 to L 12 formed by cementing three lens elements. A space between the first lens group G 1 and the second lens group G 2 is set as the maximum inter-lens space (the maximum air space) so that a reflection mirror 4 can be inserted. Also, the projection lens device satisfies eight conditional expressions.

1. A projection lens device comprising, in order from a magnification side:
 a first lens group having a negative refractive power; and 
 a second lens group having a positive refractive power, wherein 
 a space between the first lens group and the second lens group is set as the maximum air space in the projection lens device, 
 the projection lens device is substantially telecentric on a reduction side thereof, 
 the first lens group has at least one aspheric surface, and 
 the projection lens device satisfies the following conditional expressions (1) to (5)
   5.0 <Bf/f   (1) 
   105°<2ω  (2) 
   5.0 <d/f   (3) 
   −15.0 <f 1/ f<− 1.0  (4) 
   5.7 <f 2 /f   (5), 
 
 
     where
 f denotes a focal length of the whole system, 
 Bf denotes an air equivalent length of a back focal length of the whole system, 
 2ω denotes a field angle on the magnification side, 
 d denotes the maximum air space, 
 f 1  denotes a focal length of the first lens group, and 
 f 2  denotes a focal length of the second lens group. 
 
   
   
     2. The projection lens device according to  claim 1 , wherein
 a three-element cemented lens formed by cementing three lenses is disposed in the second lens group, and 
 two or more positive lenses made of a material having an Abbe number of 75 or more are disposed in the second lens group. 
 
   
   
     3. The projection lens device according to  claim 1 , wherein
 in one of the maximum air space and air spaces in the second lens group, a magnification-side focal point of a lens group disposed on the reduction side of the one air space exists, and 
 a lens surface adjacent to the reduction side of the magnification-side focal point is formed into a concave surface. 
 
   
   
     4. The projection lens device according to  claim 1 , wherein at least one positive lens that satisfies the following conditional expressions (6) and (7) is disposed in the first lens group:
   2.5 <fp/f< 25.0  (6) 
   45>νdp  (7), 
 
     where
 fp denotes a focal length of the positive lens in the first lens group, and 
 νdp denotes an Abbe number of the positive lens in the first lens group. 
 
   
   
     5. The projection lens device according to  claim 1 , wherein an optical path of the system is deflected by inserting a reflection mirror in an air space that satisfies the following conditional expression (8):
   6.0 <ld/f   (8), 
 
     where
 ld denotes the air space in which the reflection mirror is disposed. 
 
   
   
     6. The projection lens device according to  claim 1 , wherein at least one lens of the second lens group has at least one aspheric surface. 
   
   
     7. The projection lens device according to  claim 1 , wherein a three-element cemented lens that is formed by sandwiching a positive lens between two negative lenses is disposed in the first lens group. 
   
   
     8. The projection lens device according to  claim 1 , wherein
 a lens, on the most-magnification side, of the first lens group and an optional lens of the second lens group are aspheric lenses, and 
 correction of an image surface curvature associated with variation in projection distance is performed by moving the lens, on the most-magnification side, of the first lens group in an optical axis direction. 
 
   
   
     9. The projection lens device according to  claim 1 , wherein correction of a position of an image place associated with variation in projection distance is performed by varying the air space between the first lens group and the second lens. 
   
   
     10. A projection display apparatus comprising:
 at least one light source; 
 at least one light valve; 
 at least one illumination optical section that guides a beam emitted from the at least one light source, to the at least one light valve; and 
 the projection lens device according to  claim 1 , wherein 
 the beam emitted from the at least one light source is optically modulated by the at least one light valve and is projected onto a screen by the projection lens device.